1. Field of the Invention
This invention is directed to a wound dressing, in general, and to a wound dressing which permits the moisture and vapor transmission characteristics thereof to be coherently varied or adjusted, in particular.
2. Prior Art
Historically, wounds of both an acute and chronic nature have been treated with the traditional gauze and adhesive bandage coverings. However, in recent years, researchers have established that, in many respects, the traditional gauze and adhesive bandage coverings, as well as similar wound coverings, actually inhibit or even defeat the normal wound healing process by:
(1) Absorbing a significant amount of vital tissue fluid thereby dessicating tissue of the wound bed and, consequently, initiating dry tissue necrosis; PA0 (2) Establishing a high rate of tissue fluid evaporation with the result that the dry gauze dressing abuts against and adheres to newly forming tissue which can induce secondary trauma upon removal of the dressing; PA0 (3) Providing a portal of entry for infection causing micro-organisms into the wound; and/or PA0 (4) Enhancing the necrotizing effects of antiseptic irrigants by concentrating the active antimicrobial agent in the wound bed as a consequence of rapid evaporation of tissue fluid. PA0 (1) A moist environment is created and maintained within the wound bed which has proven to be essential to wound healing; PA0 (2) The polyurethane dressings are occlusive and, thus, help protect against secondary infection by preventing entry of micro-organisms to the wound site. PA0 (3) The inherent moisture/vapor transmission properties of the film permit moderate amounts of wound exudate and tissue fluid to pass through the film; PA0 (4) The frequency of dressing changes is dramatically reduced; and PA0 (5) A clinician can visually monitor the wound site through the transparent film.
More recently, a transparent polyurethane, semi-permeable, wound covering has been developed. This type of covering has significantly eliminated many of the shortcomings of gauze bandages. For example,
Although transparent film wound dressings represent a significant advance over previous treatment protocols and dressings, there are definite limitations of polyurethane film dressings. For example, most, if not all, manufacturers of semi-permeable, polyurethane wound dressings, use the same process. This process is to coat the surface of an extruded thin film of polyurethane with a medically approved adhesive; apply a release liner; cut the film into various sizes; package and sterilize. Unfortunately, however, the application of an adhesive to the entire surface of the film dressing greatly reduces the ability thereof to transport moisture, gas and/or vapor by as much as 50% of the capability of the uncoated polyurethane film.
The adhesive coated film also presents end user handling and application difficulties that have yet to be resolved. For example, when removed from the release liner, the fully adhesive coated film becomes very flimsy and difficult for the user to manipulate, even when using two hands. If, by chance, two adhesive coated surfaces of the film (or portions thereof) make intimate contact, separation thereof becomes virtually impossible, thus, necessitating that the film be discarded.
Moreover, dressings using fully coated films are inadequate for moderate to heavily exudating wounds. In view of the significantly reduced moisture/vapor permeability of the adhesive coated films, moderate to heavily exudating wounds quickly overwhelm the ability of the film to transport moisture and vapor at a rate which curtails or eliminates exudate pooling.
Typically, when the volume of exudate is clearly visible through the dressing, the probability then of the exudate fluid passing by and through the adhesive seal of the film dressing which is in contact with the intact skin around the wound margin is extremely high. Once the seal of the adhesive is breached, the dressing is no longer of any value.